JP2020053486A - Inductor - Google Patents

Abstract

To provide an inductor in which eddy current loss is reduced.SOLUTION: An inductor 100 comprises a core 30a including lamination parts 31a-33a where magnetic layers 41a, 42a and isolating layers 51a, 52a are laminated alternately, a coil 20 including a wound part 21 wound around the core 30a, the reel of the wound part 21 being placed substantially orthogonally to the lamination direction, and an element 40 receiving the core 30a and the coil 20. The lamination parts 31a-33a include a first lamination part 31a where the first magnetic layer 41a and the isolating layer 51a are laminated alternately, and a second lamination part 32a and a third lamination part 33a where the second magnetic layer and the isolating layer are laminated alternately. The first lamination part 31a has first and second faces orthogonal to the lamination direction and facing each other, and third and fourth faces parallel with the lamination direction and the reel direction and facing each other. The second lamination part 32a is placed on the first face, and the third lamination part 33a is placed on the second face.SELECTED DRAWING: Figure 1

Description

  The present invention relates to inductors.

  As a power inductor used for a choke coil of a DCDC converter or the like, an inductor in which a coil is sealed with a sealing material obtained by kneading a magnetic powder made of a soft magnetic alloy and a resin is widely used. For example, the inductor described in Patent Literature 1 is manufactured by forming a coil by sandwiching a coil with a pressure-molded sealing material and further pressing the coil.

JP-A-2006-193385 WO2018 / 079402

  Since the above-mentioned sealing material is obtained by kneading a magnetic powder made of a soft magnetic alloy and a resin, the ratio of the magnetic powder in the sealing material is low, so that the relative permeability is low. Therefore, the inductor whose coil is sealed with the sealing material cannot have a higher inductance value than an inductor made of a single soft magnetic alloy or the like. In order to obtain a desired inductance value, it is necessary to increase the number of turns of the coil, and there is a problem that the DC resistance of the inductor tends to increase. In order to solve such a problem, Patent Literature 2 discloses an inductor in which a core in which soft magnetic layers and insulating layers are alternately stacked is disposed between the internal spaces of a coil. The inductor described in Patent Literature 2 can obtain a desired inductance value without increasing the number of turns of the coil, and can reduce eddy current loss and the like generated by a magnetic field due to a current flowing through the coil. However, in order to increase the efficiency of the DCDC converter, it is necessary to further reduce the eddy current loss.

  The present invention has been made in view of the above problems, and has as its object to provide an inductor having a core and reduced eddy current loss.

  One embodiment of the inductor of the present invention is a core including a laminated portion in which a magnetic layer and an insulating layer are alternately laminated, a wound portion wound around the core, and a pair of drawers pulled out from the wound portion. And a coil in which the winding axis of the winding portion is disposed substantially perpendicular to the laminating direction of the laminating portion, and a body having an end face facing the housing and accommodating the core and the coil. The magnetic layer includes a first magnetic layer and a second magnetic layer having a higher electrical resistivity than the first magnetic layer. The stacked unit includes a first stacked unit in which first magnetic layers and insulating layers are alternately stacked, and a second stacked unit and third stacked units in which second magnetic layers and insulating layers are alternately stacked. The first laminated portion is a first surface and a second surface that are orthogonal to the laminating direction and oppose each other, and a third surface and a fourth surface that are parallel to the laminating direction and the winding axis direction. Surface. The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the third laminated portion is disposed on the fourth surface. Placed on the surface.

  One embodiment of the inductor of the present invention is a core including a laminated portion in which magnetic layers and insulating layers are alternately laminated, a wound portion wound around the core, and a pair of drawers drawn out from the wound portion. And a coil in which the winding axis of the winding portion is disposed substantially perpendicular to the laminating direction of the laminating portion, and a body having opposing end faces and accommodating the core and the coil. The magnetic layer includes a first magnetic layer and a second magnetic layer having a higher relative magnetic permeability than the first magnetic layer. The stacked unit includes a first stacked unit in which first magnetic layers and insulating layers are alternately stacked, and a second stacked unit and third stacked units in which second magnetic layers and insulating layers are alternately stacked. The first laminated portion is a first surface and a second surface that are orthogonal to the laminating direction and oppose each other, and a third surface and a fourth surface that are parallel to the laminating direction and the winding axis direction. Surface. The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the third laminated portion is disposed on the fourth surface. Placed on the surface.

  According to the present invention, it is possible to provide an inductor in which eddy current loss is reduced while having a core.

FIG. 2 is a schematic transparent perspective view of the inductor according to the first embodiment. FIG. 2 is a schematic sectional view of the inductor of FIG. 1. FIG. 14 is a schematic perspective view illustrating an example of a core of an inductor according to a fourth embodiment. FIG. 13 is a schematic sectional view of an inductor according to a fifth embodiment. FIG. 14 is a schematic perspective view illustrating an example of a core of an inductor according to a sixth embodiment. FIG. 16 is a schematic perspective view illustrating an example of a core of an inductor according to a seventh embodiment. FIG. 21 is a schematic perspective view illustrating an example of a core of an inductor according to an eighth embodiment.

  The inductor according to the present embodiment includes a core including a laminated portion in which a magnetic layer and an insulating layer are alternately laminated, a wound portion wound around the core, and a pair of lead portions pulled out from the wound portion. And a body having an end surface facing the core and accommodating the core and the coil. The coil is arranged so that the winding axis of the winding portion is substantially perpendicular to the lamination direction of the lamination portion. Further, the magnetic layer includes a first magnetic layer and a second magnetic layer having a higher electric resistivity than the first magnetic layer. The stacked unit includes a first stacked unit in which first magnetic layers and insulating layers are alternately stacked, and a second stacked unit and third stacked units in which second magnetic layers and insulating layers are alternately stacked. The first laminated portion is a first surface and a second surface that are orthogonal to the laminating direction and oppose each other, and a third surface and a fourth surface that are parallel to the laminating direction and the winding axis direction. Surface. The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the third laminated portion is disposed on the third surface. It is arranged on the fourth surface.

  In the inductor, the core is formed of a laminated portion formed by laminating a magnetic layer and an insulating layer, and the laminating direction of the laminated portion, that is, the thickness direction of the magnetic layer is substantially orthogonal to the winding axis of the winding portion of the coil. It is arranged in the internal space of the unit. In the laminated portion, the second laminated portion and the third laminated portion formed from the second magnetic layer having a higher electric resistivity than the first magnetic layer are separated from the first magnetic layer having a lower electric resistivity than the second magnetic layer. It is arrange | positioned on the outer surface of the 1st laminated part formed, and is close to the conductor of a winding part. In the second laminated portion and the third laminated portion, since the electric resistivity of the second magnetic layer is large, the eddy current generated in the cross section of the magnetic layer orthogonal to the magnetic path is reduced, and the first magnetic layer having the small electric resistivity is reduced. The eddy current loss can be reduced as compared with the case where the coil is arranged close to the winding part of the coil. This reduces the eddy current loss in the second and third laminated portions through which the magnetic flux passes, especially when the DCDC converter is under a light load when the inductor is used in the choke coil of the DCDC converter.

  An inductor includes a core including a laminated portion in which a magnetic layer and an insulating layer are alternately laminated, a coil including a wound portion wound around the core and a pair of lead portions pulled out from the wound portion, A core having a core and the coil; The coil is arranged so that the winding axis of the winding portion is substantially perpendicular to the lamination direction of the lamination portion. The magnetic layer includes a first magnetic layer and a second magnetic layer having a higher relative magnetic permeability than the first magnetic layer. The stacked unit includes a first stacked unit in which first magnetic layers and insulating layers are alternately stacked, and a second stacked unit and third stacked units in which second magnetic layers and insulating layers are alternately stacked. The first laminated portion is a first surface and a second surface that are orthogonal to the laminating direction and oppose each other, and a third surface and a fourth surface that are parallel to the laminating direction and the winding axis direction. Surface. The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the third laminated portion is disposed on the fourth surface. Placed on the surface. Since the relative permeability of the second magnetic layer is large in the second laminated portion and the third laminated portion, the eddy current generated in the cross section of the magnetic layer orthogonal to the magnetic path is reduced, and the first magnetic layer having a small relative permeability is reduced. The eddy current loss can be reduced as compared with the case where the coil is arranged close to the winding part of the coil.

  In the laminated portion of the inductor, the product of the electric resistivity of the second magnetic layer and the relative magnetic permeability may be larger than the product of the electric resistivity of the first magnetic layer and the relative magnetic permeability. As a result, eddy current loss that occurs in the inductor at a light load when the DC superimposed current flowing through the inductor is small can be reduced.

  In the inductor, a pair of lead portions is pulled out from the outer periphery of the winding portion in the direction of the facing end surface of the element body, and in a cross section parallel to the end surface, the number of coil turns of the winding portion on the side from which the drawing portion is pulled out. Is one turn more than the side opposite to the side from which the drawer is pulled out, so that the number of laminations of the second magnetic layer in the second lamination and the number of lamination of the second magnetic layer in the third lamination are It may be different. When the pair of lead portions are pulled out from the outer periphery of the winding portion in the opposite end surface directions of the element body in the opposite directions, the second stacked portion or the second stacked portion disposed on one of the drawn portion sides By increasing the number of stacked magnetic layers, the eddy current loss under light load can be reduced more effectively.

  At least two of the first stacked unit, the second stacked unit, and the third stacked unit may have different stacking directions. For example, by arranging the lamination direction of the second and third lamination portions and the lamination direction of the first lamination portion substantially at right angles, for example, eddy current loss at light load can be more effectively reduced. can do.

  At least one of the first stacked unit, the second stacked unit, and the third stacked unit may be divided by at least one surface orthogonal to the winding axis direction of the winding unit. For example, by dividing at least one of the second laminated portion and the third laminated portion by at least one surface orthogonal to the direction of the winding axis of the winding portion, the eddy current at light load can be more effectively achieved. Loss can be reduced.

  The thickness of the first magnetic layer and the thickness of the second magnetic layer may be different. In this case, in the core, a value obtained by dividing the square of the thickness of the second magnetic layer by the square root of the product of the relative magnetic permeability and the electric resistivity of the second magnetic layer is obtained by dividing the square of the thickness of the first magnetic layer by the first magnetic layer. It may be smaller than a value obtained by dividing by the square root of the product of the relative magnetic permeability and the electric resistivity of the layer. The eddy current loss is proportional to the square of the thickness of the magnetic layer, and is inversely proportional to the square root of the product of the relative magnetic permeability and the electric resistivity of the magnetic layer. Current loss can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies an inductor for embodying the technical idea of the present invention, and the present invention is not limited to the inductor described below. Note that the members described in the claims are not limited to the members of the embodiment. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention thereto, unless otherwise specified. It is only an example. In addition, the size, positional relationship, and the like of the members illustrated in each drawing may be exaggerated for clarity of description. Further, in the following description, the same names and reference numerals denote the same or similar members, and a detailed description thereof will be appropriately omitted. Still further, each element constituting the present invention may be configured such that a plurality of elements are formed of the same member and one member also serves as the plurality of elements, or conversely, the function of one member may be a plurality of members. It can also be realized by sharing. In addition, the contents described in some embodiments can be used in other embodiments. In the second and subsequent embodiments, description of matters common to the first embodiment will be omitted, and only different points will be described. In particular, the same operation and effect of the same configuration will not be sequentially described for each embodiment.

(Example 1)
First Embodiment An inductor 100 according to a first embodiment will be described with reference to FIGS. FIG. 1 is a schematic transparent perspective view showing an example of the inductor 100. FIG. 2 is a schematic cross-sectional view of inductor 100 taken along a line AA in FIG. 1 and parallel to the winding axis of the coil.

  As shown in FIG. 1, the inductor 100 includes a coil 20 including a winding part 21 and a pair of lead parts 22 a and 22 b drawn from the winding part 21, and a core 30 a surrounded by the winding part 21 of the coil 20. And a body 40 accommodating the coil 20 and the core 30a, and a pair of external terminals 60 electrically connected to the lead portions 22a and 22b, respectively. The outer peripheral shape of the winding portion 21 as viewed from the winding axis direction Z is an elliptical shape having a major axis and a minor axis or an elliptical shape. The element body 40 has a bottom surface on the mounting surface side, a top surface facing the bottom surface, and a pair of end surfaces 70 and a pair of side surfaces 72 adjacent to the bottom surface and the top surface and facing each other. The pair of end surfaces 70 are substantially orthogonal to the long axis direction of the winding portion 21, and the pair of side surfaces 72 are substantially orthogonal to the short axis direction of the winding portion 21. The element body 40 has a longitudinal direction L parallel to the long axis direction in a cross section orthogonal to the winding axis of the winding portion 21 and a short direction W parallel to the short axis direction orthogonal to the long axis direction of the winding portion 21. And a height direction H of the body parallel to the winding axis direction Z.

  The element body 40 is formed by applying pressure to the composite material in which the coil 20 and the core 30a are embedded. The composite material forming the element body 40 includes, for example, a magnetic powder and a binder such as a resin. Examples of the magnetic powder include iron-based metals such as iron (Fe), Fe-Si, Fe-Si-Cr, Fe-Si-Al, Fe-Ni-Al, and Fe-Cr-Al. Magnetic powder, metal magnetic powder of a composition not containing iron, metal magnetic powder of another composition containing iron, metal magnetic powder in an amorphous state, metal magnetic powder whose surface is covered with an insulator such as glass, Modified metallic magnetic powder, nanocrystalline metallic magnetic powder, polycrystalline metallic magnetic powder, ferrite powder and the like can be used. Further, as the binder, a thermosetting resin such as an epoxy resin, a polyimide resin, and a phenol resin, and a thermoplastic resin such as a polyester resin and a polyamide resin are used.

  The coil 20 is formed by winding a conducting wire having a rectangular cross section (hereinafter, also referred to as a flat wire) having an insulating coating, with the lead portions 22a and 22b positioned on the outer periphery and the winding portion 21 wound in two spiral steps. ing. The winding part 21 has a space for accommodating the core 30 a inside the winding part 21 around which the conductive wire is wound, and the winding axis is substantially orthogonal to the bottom surface and the top surface of the element body 40, and Are located. The pair of lead portions 22a and 22b are pulled out from the outermost periphery of the winding portion in opposite directions toward the end face 70 in the longitudinal direction L of the body 40, and are drawn out from the respective end faces 70 of the body 40. Parts of 22a and 22b are exposed. External terminals 60 that are electrically connected to the lead portions 22a and 22b exposed from the element body 40 are provided on the end face 70 and a part of the bottom surface of the element body 40, respectively.

  The core 30a has a first laminated portion 31a in which first magnetic layers 41a and insulating layers 51a are alternately laminated, a thickness and a relative magnetic permeability equal to those of the first magnetic layer, and an electric resistivity larger than that of the first magnetic layer. A second laminated portion 32a in which the second magnetic layer 42a and the insulating layer 52a are alternately laminated, and a third laminated portion 33a in which the second magnetic layer 42a and the insulating layer 53a are alternately laminated are provided. Each of the first stacked portion 31a, the second stacked portion 32a, and the third stacked portion 33a (hereinafter, also simply referred to as a stacked portion) has a rectangular parallelepiped shape. The first stacked portion 31a is located on the outermost layer orthogonal to the stacking direction, and is adjacent to the first and second surfaces facing each other, and adjacent to the first and second surfaces, and It is a surface parallel to the direction and the winding axis direction, and has a third surface and a fourth surface facing each other, and two other side surfaces. In the inductor 100, the second laminated portion 32a, the first laminated portion 31a, and the third laminated portion 33a are laminated in this order with the lamination direction being the same to form the core 30a. That is, the second stacked unit 32a and the third stacked unit 33a are arranged on the first and second surfaces of the first stacked unit 31a that face each other so that the stacking directions are parallel. The core 30 a is accommodated in the internal space of the winding part 21 with the laminating direction substantially orthogonal to the winding axis of the winding part 21. In the core 30a, the second laminated portion 32a and the third laminated portion 33b formed from the second magnetic layer having a large electric resistivity are arranged closer to the conductor forming the winding portion 21 than the first laminated portion. You.

  As shown in FIG. 2, the core 30a and the coil winding portion 21 are housed inside the element body 40, and the coil winding portion 21 is provided outside the second stacked portion 32a and the third stacked portion 33a of the core 30a. The constituent wires are arranged close to each other. In FIG. 2, the height of the core 30a and the height of the winding portion 21 are substantially the same. The core 30a is formed by laminating a first laminated portion 31a in which a first magnetic layer 41a and an insulating layer 51a are laminated, and a second magnetic layer 42a and an insulating layer 52a having a higher electric resistivity than the first magnetic layer 41a. It is formed of a second laminated portion 32a and a third laminated portion 33a in which the second magnetic layer 42a and the insulating layer 53a are laminated. The lamination directions of the first laminated section 31a, the second laminated section 32a, and the third laminated section 33a are all the same. The outermost layer of the second laminated portion 32a and the third laminated portion 33a is the second magnetic layer 42a. Further, the second laminated portion 32a and the third laminated portion 33a are respectively disposed on the outermost layer surfaces on both sides in the laminating direction of the first laminated portion 31a, and are closer to the conductor of the winding portion 21 than the first laminated portion 31a. Placed. Insulating layers 54a and 55a are respectively arranged between the first laminated portion 31a and the second laminated portion 32a and the third laminated portion 33a.

  The first magnetic layer 41a and the second magnetic layer 42a are formed, for example, with substantially the same thickness, have a thin plate shape, and have at least different electrical resistivity. The first magnetic layer 41a and the second magnetic layer 42a may have, for example, substantially the same relative magnetic permeability. The first magnetic layer 41a and the second magnetic layer 42a are selected, for example, from the group consisting of iron, silicon steel, permalloy, sendust, permendur, soft ferrite, amorphous magnetic alloy, nanocrystalline magnetic alloy, and alloys thereof. It is a soft magnetic material. The first magnetic layer 41a and the second magnetic layer 42a may be formed using other materials as long as they have a higher relative magnetic permeability than the composite material constituting the element body 40. Good. The insulating layer electrically insulates and bonds the first magnetic layer 41a and the second magnetic layer 42a, and also electrically insulates and bonds between the laminated portions. In FIG. 2, each insulating layer has substantially the same thickness. The insulating layer is formed of, for example, a material containing at least one selected from the group consisting of an epoxy resin, a polyimide resin, and a polyimide amide resin.

  The second magnetic layer 42a has a higher electrical resistivity than the first magnetic layer 41a. The ratio of the electrical resistivity of the second magnetic layer 42a to the first magnetic layer 41a is, for example, greater than 1, and preferably 1.3 or more.

  The thickness ratio (b / a) of the thickness b of the insulating layer to the thickness a of the magnetic layer of each of the first laminated portion 31a, the second laminated portion 32a, and the third laminated portion 33a is, for example, 0.2 or less. Is about several μm. Here, an example of a method for obtaining the thickness ratio will be described. The thickness ratio (b / a) is determined by dividing the thickness b of the insulating layer by the thickness a of the magnetic layer constituting the laminated portion. The thicknesses a and b are measured by measuring the thicknesses of all the magnetic layers 41a and 42a and the thicknesses of all the insulating layers 51a on a straight line substantially at the center of the core in the stacking direction in the cross-sectional observation image at the substantially center of the core. , As an average of the measured values.

  Generally, the loss in an inductor is divided into copper loss due to a winding conductor forming a coil and iron loss which is a sum of eddy current loss and hysteresis loss due to a core. When the load is light, the DC superimposed current is small, and the magnetic flux is concentrated at a position near the conductor forming the winding portion. Under heavy load, the DC superimposed current is large, and the magnetic flux spreads far from the conductor.

  In the inductor 100, since the core 30a is arranged in the internal space of the winding portion 21, the light is applied to the second stacked portion 32a and the third stacked portion 33a on the side closer to the conductor of the winding portion 21 of the core 30a at a light load. Although the magnetic flux density causing the eddy current increases, the electric resistivity of the second magnetic layer 42a is larger than that of the first magnetic layer 41a, so that the eddy current loss is reduced and the iron loss is reduced. On the other hand, at the time of heavy load, the magnetic flux densities in the second laminated portion 32a, the third laminated portion 33a, and the first laminated portion 31a are all high, but the copper loss due to the increase of the DC superimposed current is further increased. Becomes relatively small. Therefore, in the inductor 100 having the above-described configuration, the eddy current loss is reduced particularly at a light load while having the core.

Table 1 shows a core obtained by laminating a second laminated portion including a magnetic layer b and an insulating layer, a first laminated portion including a magnetic layer a and an insulating layer, and a third laminated portion including a magnetic layer b and an insulating layer in this order. With respect to the inductor of Example 1 used, the DC superimposed current was 0 A, the amplitude of the AC current was 10 mA, the electric resistivity ρ _a of the magnetic layer _a was fixed, and the electric resistivity ρ _b of the magnetic layer _b was changed. And results obtained by simulating the eddy current loss Pe. In the inductor according to the first embodiment, the relative magnetic permeability of the magnetic layer a and the magnetic layer b are equal to each other, the magnetic layers a and b have the saturation magnetic flux density Bs = 1.0T, and the size of the element body L × W × H was 2.0 mm × 1.6 mm × 1.0 mm, and the number of turns of the winding was 8.5. The DC superimposed saturation current was a DC superimposed current value that was 30% lower than the inductance value of the DC superimposed current of 0. The simulation was performed by a harmonic magnetic field analysis at a frequency of 10 MHz using finite element method analysis software Femtet (registered trademark) manufactured by Murata Software.

Since the inductors of the first embodiment have the same inductance value, it can be considered that the inductors have the same characteristics except for the eddy current loss. The results of Example 1 show that the eddy current loss is reduced as the electric resistivity ρ _b of the magnetic layer _b becomes larger than the electric resistivity ρ _a of the magnetic layer a. In other words, by arranging the magnetic layer having a high electric resistivity close to the winding portion, it is possible to reduce the eddy current loss while maintaining the inductance value.

(Example 2)
The inductor according to the second embodiment has the same configuration as the inductor 100 according to the first embodiment except that the relative magnetic permeability of the second magnetic layer is larger than the relative magnetic permeability of the first magnetic layer. In the inductor according to the second embodiment, the electrical resistivity of the second magnetic layer may be substantially the same as the electrical resistivity of the first magnetic layer.

Table 2 shows a core obtained by laminating a second laminated portion including a magnetic layer b and an insulating layer, a first laminated portion including a magnetic layer a and an insulating layer, and a third laminated portion including a magnetic layer b and an insulating layer in this order. When the superposed DC current is 0 A and the amplitude of the AC current is 10 mA, the thickness and the number of layers of the magnetic layers a and b, the relative magnetic permeability and the electric resistivity are changed with respect to an inductor having a different laminated portion configuration. The results obtained by simulating the inductance value and the eddy current loss Pe of FIG. In the inductors of Examples 2a to 2c, the thicknesses of the magnetic layer a and the magnetic layer b are equal, and the relative magnetic permeability μ _b of the magnetic layer _b is larger than the relative magnetic permeability μ _{a of} the magnetic layer a. The electric resistivity ρ of the magnetic layer b is similarly changed. In the inductors of Examples 2d to 2f, the thickness and relative permeability μ of the magnetic layer a and the magnetic layer b are equal to each other, and the electric resistivity ρ of the magnetic layer a and the magnetic layer b is similarly changed. .

  In Examples 2a to 2f, there is no significant difference in the inductance value, so that the characteristics other than the eddy current loss can be regarded as the same inductor. Comparing Example 2a and Example 2d, Example 2b and Example e, and Example 2c and Example 2f, when the electrical resistivity of the magnetic layer is the same, the relative permeability of the magnetic layer b is changed to the magnetic permeability. It can be seen that the eddy current loss is reduced by increasing the relative magnetic permeability of the layer a. That is, since the second laminated portion and the third laminated portion in which the second magnetic layer having a large relative magnetic permeability is laminated are disposed close to the winding portion, eddy current loss particularly at a light load is reduced. You.

Here, the eddy current loss of the inductor will be described.
In general, in the inductor, the eddy current loss Pe in the magnetic layer of the core formed by laminating the magnetic layer and the insulating layer is such that when the thickness t of the magnetic layer is sufficiently smaller than the width in the surface direction of the flat magnetic layer, Assuming that the electrical resistivity of the magnetic layer is ρ and the relative magnetic permeability is μ, it is proportional to the square of the thickness t and inversely proportional to the square root of the product of the electrical resistivity ρ and the relative magnetic permeability μ. That is, the eddy current loss Pe is expressed by the following equation (1).

  For example, in the inductor 100 according to the first embodiment, the eddy current loss generated in the second stacked portion and the third stacked portion is made smaller than the eddy current loss generated in the first stacked portion. Only the electric resistivity of the magnetic layer was increased. However, from the equation (1), in order to make the eddy current loss generated in the second and third stacked portions smaller than the eddy current loss generated in the first stacked portion, the square of the thickness of the second magnetic layer must be equal to the second magnetic layer. The value obtained by dividing the square of the thickness of the first magnetic layer by the square root of the product of the relative permeability of the first magnetic layer and the electrical resistivity is smaller than the value obtained by dividing the square root of the product of the relative magnetic permeability and the electrical resistivity of the layer. It turns out that it is good to be small. That is, in addition to making the electric resistivity of the second magnetic layer larger than the electric resistivity of the first magnetic layer, it is possible to further reduce the eddy current loss by changing the relative permeability of each magnetic layer. it can.

(Example 3)
The inductor according to the third embodiment is different from the inductor according to the third embodiment except that the product of the electrical resistivity of the second magnetic layer and the relative magnetic permeability is larger than the product of the electrical resistivity of the first magnetic layer and the relative magnetic permeability. The configuration is the same as that of the first inductor 100. The first magnetic layer and the second magnetic layer have the same thickness and the same relative magnetic permeability. In the inductor of the third embodiment, the first magnetic layer and the second magnetic layer may have different electrical resistivity and relative magnetic permeability, and the first magnetic layer and the second magnetic layer have substantially the same electrical resistivity. The relative magnetic permeability may be different, the first magnetic layer and the second magnetic layer may have substantially the same relative magnetic permeability, and may have different electrical resistivity.

  In the inductor according to the third embodiment, the second laminated portion and the third laminated portion in which the second magnetic layer having the product of the electric resistivity and the relative magnetic permeability is larger than the first magnetic layer are laminated on the conductor of the winding portion. Since they are arranged close to each other, eddy current loss particularly at light load is reduced.

(Example 4)
The configuration of the core 30f included in the inductor of the fourth embodiment will be described with reference to FIG. In the core 30f, except that the thickness of the first magnetic layer 41f constituting the first laminated portion 31f is different from the thickness of the second magnetic layer 42f constituting the second laminated portion 32f and the third laminated portion 33f. , The inductor 100 of the first embodiment, the inductor of the second embodiment, or the inductor of the third embodiment.

In the core 30f, the first laminated portion 31f is formed by laminating the first magnetic layer 41f and the insulating layer 51f in the W direction orthogonal to the longitudinal direction L of the element body and the winding axis direction Z of the coil.
The second laminated portion 32f is configured such that the second magnetic layer 42f and the insulating layer 52f are laminated in the lateral direction W of the element body, and the third laminated portion 33f is configured such that the second magnetic layer 42f and the insulating layer 53f are composed of the element body. It is formed by being laminated in the short direction W direction. The second laminated portion 32f and the third laminated portion 33f are arranged on the outermost layer surfaces on both sides in the laminating direction of the first laminated portion 31f via insulating layers 54f and 55f, respectively. In the core 30f, the thickness of the second magnetic layer 42f is formed to be thinner than the thickness of the first magnetic layer 41f, and the square of the thickness of the second magnetic layer 42f is calculated as the square of the relative magnetic permeability and electric resistivity of the second magnetic layer 42f. The value divided by the square root of the product is smaller than the value obtained by dividing the square of the thickness of the first magnetic layer 41f by the square root of the product of the relative magnetic permeability and the electric resistivity of the first magnetic layer 41f. Thereby, the eddy current loss at the time of light load can be reduced more effectively.

(Example 5)
Fourth Embodiment An inductor 110 according to a fourth embodiment will be described with reference to FIG. FIG. 4 is a schematic sectional view of the inductor 110 at the same position as AA in FIG. In the inductor 110, in the core 30b, the number of laminations of the second magnetic layer 42a in the third laminated portion 33b disposed close to the side 21a from which the end of the coil of the wound portion 21 is drawn out is the second laminated portion 32b The configuration is the same as that of the inductor 100 of the first embodiment, the inductor of the second embodiment, or the inductor of the third embodiment, except that the number of layers is larger than the number of layers in.

  When the pair of drawers are drawn toward the end faces of the element body facing each other, the winding portions are not bilaterally symmetric in a cross section parallel to the end faces. That is, in the cross-sectional view of FIG. 4, when the lead portion is pulled out from the right side 21 a of the winding portion 21, the right side 21 a of the winding portion 21 is one turn longer than the left side 21 b of the winding portion 21. It will be wound many times. As a result, the right side 21a of the winding portion 21 has a higher magnetic flux density than the left side 21b of the winding portion 21. In the inductor 110, the number of laminations of the second magnetic layer 42a is different between the second lamination 32b and the third lamination 33b, and the number of laminations in the third lamination 33b disposed on the right side 21a of the winding part 21 is larger. More. With this configuration, it is possible to more effectively reduce the loss that occurs in inductor 110 at a light load. Note that, after being pulled out in the direction of the facing end surface, the lead portion of the coil may be exposed on the facing end surface, or may be bent and exposed on the bottom surface of the element body.

(Example 6)
The configuration of the core 30c included in the inductor of the sixth embodiment will be described with reference to FIG. In the inductor according to the sixth embodiment, the point that the stacking direction of the first stacked portion 31c in the core 30c and the stacking direction of the second stacked portion 32c and the third stacked portion 33c are substantially orthogonal to each other is different from the inductor 100 according to the first embodiment. Unlike the inductor of the second embodiment or the inductor of the third embodiment, the other configuration is the same as that of the inductor 100 of the first embodiment, the inductor of the second embodiment, or the inductor of the third embodiment.

  In the core 30c, the first laminated portion 31c is formed by laminating the first magnetic layer 41c and the insulating layer 51c in the lateral direction W of the element body. In the second laminated portion 32c, the second magnetic layer 42c and the insulating layer 52c are laminated in the longitudinal direction L of the body, and in the third laminated portion 33c, the second magnetic layer 42c and the insulating layer 53c are formed of the body. It is formed by being laminated in the longitudinal direction L. The second laminated portion 32c and the third laminated portion 33c are disposed on the outermost layer surfaces on both sides of the first laminated portion 31c in the laminating direction via insulating layers 54c and 55c, and are disposed on both sides of the first laminated portion 31c in the laminating direction. Covers the outermost surface. The number of laminations of the second magnetic layer 42c in the second lamination 32c and the third lamination 33c is the number of laminations of the second magnetic layer 42a in the second lamination 32a and the third lamination 33a of the core 30a of the first embodiment. However, the width (W direction) of the magnetic layer perpendicular to the magnetic path is also smaller. Since the eddy current loss is also proportional to the width (W direction) of the magnetic layer orthogonal to the magnetic path, the eddy current loss of the inductor at light load is further reduced.

(Example 7)
A configuration of a core 30d included in the inductor of the seventh embodiment will be described with reference to FIG. In the inductor according to the seventh embodiment, the stacking direction of the first stacked portion 31d in the core 30d is substantially parallel to the longitudinal direction L of the element body, and is orthogonal to the stacking direction of the second stacked portion and the third stacked portion. Except for this point, the configuration is the same as that of the inductor 100 of the first embodiment, the inductor of the second embodiment, or the inductor of the third embodiment.

In the core 30d, the first laminated portion 31d is formed by laminating the first magnetic layer 41d and the insulating layer 51d in the longitudinal direction L of the element body. The second laminated portion 32d is formed by laminating a second magnetic layer 42d and an insulating layer 52d in the lateral direction W of the element body. Are laminated in the lateral direction W of the element body. The second stacked portion 32d and the third stacked portion 33d are adjacent to the outermost layer surfaces on both sides in the stacking direction of the first stacked portion 31d, are surfaces parallel to the winding axis direction, and are side surfaces facing each other. On the third and fourth surfaces, insulating layers 54d and 55d are interposed to cover the opposing side surfaces of the first laminated portion 31d.
The number of stacked first magnetic layers 41d in the first stacked portion 31d is larger than the number of stacked first stacked portions 31a of the core 30a of the first embodiment, but the width of the magnetic layer orthogonal to the magnetic path (W Direction) is smaller. Therefore, the eddy current loss generated at the end faces facing each other in the longitudinal direction L can be reduced, and the loss of the inductor at light load is reduced.

(Example 8)
The configuration of the core 30e included in the inductor of the eighth embodiment will be described with reference to FIG. In the core 30e, except that the second laminated portion 32e and the third laminated portion 33e are respectively divided by gap portions 44e and 45e substantially orthogonal to the winding axis direction Z, the inductor 100 of the first embodiment and the third embodiment are different from each other. The configuration is the same as that of the second inductor or the third embodiment.

  In the core 30e, the first laminated portion 31e is formed by laminating the first magnetic layer 41e and the insulating layer 51e in the lateral direction W of the element body. The second laminated portion 32e is formed by laminating the second magnetic layer 42e and the insulating layer 52e in the lateral direction W of the body, and the third laminated portion 33e is formed by combining the second magnetic layer 42e and the insulating layer 53e with the body. It is formed by being laminated in the short direction W. The second stacked unit 32e and the third stacked unit 33e are disposed on the outermost layer surfaces on both sides in the stacking direction of the first stacked unit 31e via insulating layers 54e and 55e. Further, the second stacked portion 32e is divided by a gap portion 44e orthogonal to the winding axis direction Z, and the third stacked portion 33e is split by a gap portion 45e orthogonal to the winding axis direction Z. The gap portions 44e and 45e extend to the outer peripheral portion in each of the second stacked portion 32e and the third stacked portion 33e, and the side surfaces of the second stacked portion 32e and the third stacked portion 33e and the outermost layer surfaces on both sides in the stacking direction. It is exposed from. The gap portions 44e and 45e are formed of a material that bonds the divided second laminated portion 32e and third laminated portion 33e, respectively. The gaps 44e and 45e are formed of a material having a lower relative magnetic permeability than the second magnetic layer 42e. Further, the relative magnetic permeability of the gap portions 44e and 45e may be lower than the relative magnetic permeability of the element body, or may be a non-magnetic material.

  In the second laminated portion 32e and the third laminated portion 33e, the gap portions 44e and 45e function as magnetic gaps orthogonal to the winding axis direction Z, and the magnetic resistance in the winding axis direction is increased. Thereby, the eddy current loss is further reduced.

In the inductor 100, the conductor forming the coil is a rectangular wire, but may be a conductor having a substantially circular or polygonal cross section.
In the inductor 100, the outer shape of the winding portion of the coil as viewed from the winding axis direction is an ellipse or an ellipse, but may be a circle, a rectangle, a polygon, or the like. The winding portion of the coil is formed in a so-called α-winding shape (for example, see Japanese Patent Application Laid-Open No. 2009-239076) in which a conductive wire is wound in two steps, and is formed by an edgewise winding, a plated conductor pattern, or the like. It may be formed.
In the inductor 100, both ends of the coil are drawn out in the direction of the end face of the body, but may be drawn out in the side direction of the body.
In the inductor 100, the height of the core and the height of the winding portion are substantially the same, but the height of the core may be higher or lower than the height of the winding portion.
In the inductor 100, the first magnetic layer and the second magnetic layer may have different thicknesses.
In the core 30e according to the eighth embodiment, the gap portion is provided in the second stacked portion and the third stacked portion. However, the gap portion may be provided in the first stacked portion, and any one of the second stacked portion and the third stacked portion may be provided. A gap may be provided only on one side.
In the inductor according to the sixth or seventh embodiment, a gap may be provided in at least one of the first, second, and third stacked units, similarly to the core 30e according to the eighth embodiment.
In the inductors of the first to eighth embodiments, the core has a rectangular parallelepiped shape, but at least one of the sides of the core may be removed by a flat surface or a curved surface.
Although the core has the second laminated portion, the first laminated portion, and the third laminated portion laminated in this order, it may be only one of the second laminated portion and the third laminated portion.

20 Coil 21 Winding part 22a, 22b Pull-out part 30a, 30b, 30c, 30d, 30e Core 31a, 32a, 33a 31b, 32b, 33b, 31c, 32c, 33c, 31d, 32d, 33d, 31e, 32e, 33e, 31f, 32f, 33f Laminated part 40 Element body 41a, 42a, 41c, 42c, 41d, 42d, 41e, 42e, 41f, 42f Magnetic layer 44e, 45e Gap part 51a, 52a, 53a, 54a, 55a Insulating layer 60 External terminal 100, 110 inductor

Claims (7)

A core including a laminated portion in which a magnetic layer and an insulating layer are alternately laminated,
A coil including a wound portion wound around the core and a pair of drawn portions pulled out from the wound portion, wherein a winding axis of the wound portion is disposed substantially orthogonal to a stacking direction of the stacked portion; When,
A body having opposing end faces and housing the core and the coil;
With
The magnetic layer includes a first magnetic layer and a second magnetic layer having a higher electric resistivity than the first magnetic layer,
The laminated portion includes a first laminated portion in which the first magnetic layer and the insulating layer are alternately laminated, and a second laminated portion and a third laminated portion in which the second magnetic layer and the insulating layer are alternately laminated. Including
The first laminated portion is a first surface and a second surface orthogonal to the laminating direction and opposed to each other, and a third surface and a fourth surface parallel to the laminated direction and the winding axis direction. With the surface of
The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the second laminated portion is disposed on the third surface. The three stacked portions are inductors arranged on the fourth surface. A core including a laminated portion in which a magnetic layer and an insulating layer are alternately laminated,
A coil including a wound portion wound around the core and a pair of drawn portions pulled out from the wound portion, wherein a winding axis of the wound portion is disposed substantially orthogonal to a stacking direction of the stacked portion; When,
A body having opposing end faces and housing the core and the coil;
With
The magnetic layer includes a first magnetic layer and a second magnetic layer having a higher relative magnetic permeability than the first magnetic layer,
The laminated portion includes a first laminated portion in which the first magnetic layer and the insulating layer are alternately laminated, and a second laminated portion and a third laminated portion in which the second magnetic layer and the insulating layer are alternately laminated. Including
The first laminated portion is a first surface and a second surface orthogonal to the laminating direction and opposed to each other, and a third surface and a fourth surface parallel to the laminated direction and the winding axis direction. With the surface of
The second laminated portion is disposed on the first surface, the third laminated portion is disposed on the second surface, or the second laminated portion is disposed on the third surface, and the second laminated portion is disposed on the third surface. The three stacked portions are inductors arranged on the fourth surface.   3. The inductor according to claim 1, wherein a product of an electric resistivity of the second magnetic layer and a relative magnetic permeability is larger than a product of an electric resistivity of the first magnetic layer and a relative magnetic permeability. The pair of pull-out portions are pulled out from the outer periphery of the winding portion in the direction of opposed end faces of the body, respectively,
4. The inductor according to claim 1, wherein the number of laminated second magnetic layers in the second laminated portion is different from the number of laminated second magnetic layers in the third laminated portion. 5.   5. The inductor according to claim 1, wherein at least two of the first, second, and third laminated portions have different laminating directions. 6.   The at least one of the first laminated portion, the second laminated portion, and the third laminated portion is divided by at least one surface substantially orthogonal to a winding axis direction of the winding portion. The inductor according to any one of the above. The core has a value obtained by dividing the square of the thickness of the second magnetic layer by the square root of the product of the relative magnetic permeability and the electric resistivity of the second magnetic layer,
The inductor according to any one of claims 1 to 6, wherein the square of the thickness of the first magnetic layer is smaller than a value obtained by dividing the square of the product of the relative magnetic permeability and the electrical resistivity of the first magnetic layer.

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